The invention relates to a device for separating a mass flow containing coarse and fine particles as gravel and sand and a sludge with ultrafine particles as laitance into its components.
A device for this purpose is known which comprises a trough and a screw conveyor therein. The axis of the conveyor is inclined under 30 degrees. In the lower part of the trough a water chamber is formed. The mass is fed into the water chamber and the sludge is discharged therefrom. The coarse and fine particles are transported upwards but only the coarse particles are discharged at the upward end of the trough, because the fine particles again and again are rinsed back. The known device is used for reprocessing leftover and returned concrete especially in the ready-mix concrete industry. In the concrete production coarse particles have granular sizes between 4 and 32 mm, fine particles between 0.2 and 4 mm and ultrafine particles between 0 and 0.2 mm. In the known device the so called screen cut lies in the range between 0.5 and 1.5 mm depending on the fed amount of mass per time unit. The known device is subjected to a remarkable wear because gravel is clamped between the rotating conveyor screw and the stationary trough. The device produces an excessive noise and requires a great driving energy because of the breaking of the clamped gravel.